ES2425443T3 - System to produce safe images and method to form an ink powder - Google Patents

Abstract

A system for producing a secure electrophotographic image, such that the system comprises a substrate and an ink powder that work together to produce a printed image on a first surface of the substrate and an indelible copy of the image, underlying the image printed on the substrate, so that the ink powder has the form of micronized particles comprising: a thermoplastic binder resin; a dye to form an image on the first surface of the substrate; a visible pigment, configured to move or migrate through a portion of the substrate to form an indelible copy of the image on the substrate; and a migration-promoting agent, intended to favor the migration of the pigment into the substrate.

Description

System to produce safe images and method to form an ink powder

Cross Reference to Related Requests

This Application claims the benefit of the US Provisional Patent Application. Series No. 60 / 381.405, entitled METHOD AND APPARATUS FOR THE SECURE PRINTING OF INK POWDER-BASED IMAGES (“METHOD AND APPARATUS FOR SECURE PRINTING OF TONER-BASED IMAGES”), presented on May 16, 2002.

Field of the Invention

The present invention relates to a system for printing and copying documents. More particularly, the invention relates to an improved method of forming an ink powder in order to print or copy documents in a secure manner, so that the documents are difficult to falsify and the original versions of the documents are easily verifiable.

Background of the invention

Obtaining images of documents based on ink powder, such as electrophotographic, ionographic, magnetographic and similar imaging techniques, generally involves forming an electrostatic or magnetic image on a photoconductive, charged or magnetized plate or drum, brushing the license plate

or drum with a charged or magnetized ink powder, transfer the image onto a substrate such as paper, and melt the ink powder onto the substrate using heat, pressure and / or a solvent. Using this technique, it is possible to easily form relatively cheap images on a substrate surface.

Because obtaining images based on ink powder constitutes a relatively fast and cheap technique for producing copies of images, the technique is often used to produce documents that were being formed, in a conventional manner, with the use of other forms of printing or imaging - for example, impact printing or inkjet printing. For example, in recent years it has been used to obtain images based on ink dust to produce financial documents such as personal checks, stock certificates and banknotes; legal documents such as wills or wills and deeds; medical documents such as prescription medications and medical orders, and similar documents. Unfortunately, because the image is formed on the surface of the substrate, documents produced using imaging techniques based on ink powder are relatively easy to falsify and / or duplicate.

Various techniques for printing or forming secure documents have been developed over the years. For example, US Pat. No. 5,124,217, issued to Gruber et al. On June 23, 1992, it disclosed a secure printing ink powder for an electrophotographic treatment. This ink powder, when exposed to a solvent such as toluene, often used in document forgery, produces a stain of color indicative of the counterfeit attempt. This ink powder is only useful for exposing an attempt to counterfeit when a specific solvent is used to remove a portion of a printed image. In this way, ink powder cannot be used to reduce copying of the document or its falsification by adding material to the document.

U.S. Pat. No. 5,714,291, issued to Marianello et al. on February 3, 1998, it discloses another ink powder that includes submicron particles sensitive to ultraviolet light. The authenticity of the document can be verified using an ultraviolet scanner. The fact that it is necessary to use an ultraviolet scanner is generally undesirable because it adds a cost to the forgery analysis and requires additional equipment.

Other techniques for producing secure images include modifying the paper on which the image is printed. Such modified papers include paper that includes a low ink absorption coating and paper that includes microcapsules that can be crushed containing leucodescent ink and a color accepting agent. While the techniques that include these forms of paper work relatively well for printing or copying the type of impact, the techniques will not work well in association with ink powder based printing methods.

Other techniques for producing secure images include providing special paper coatings in order to increase the stain resistance of an image created by an electrostatic process. However, coatings do not generally affect the ability to add material to the document or to authenticate the originality of the document.

US-A-4,366,833 discloses a method for making security documents using an electrophotographic printer, in particular a photocopier or a laser printer, which includes the step of exposing the printed image to a liquid accelerating agent or steam. Under the influence of the accelerating agent, a second pigment contained in the ink powder that is used to produce the image migrates within the document, so that a second image is produced on the paper, facing or framed with the printed image. The procedure is applicable to images created on paper, security paper and synthetic papers.

EP 1,095,991 discloses a double color ink that is applied to a substrate by means of writing utensils such as markers, felt tip pens and the like.

For the above reasons, improved methods and apparatus for forming secure documents using an ink powder based treatment, which are relatively simple and cheap, are desirable.

Summary of the invention

Accordingly, an ink powder is provided to produce a secure image on a substrate, as well as a method of forming said ink powder, as defined in the accompanying claims. The present invention provides an improved ink powder to produce safe images, as well as improved methods for forming and using the ink powder. In addition to addressing the various disadvantages of ink powders and methods known herein, in general, the invention provides an ink powder that produces images that are difficult to alter and for which it is easy to visually assert whether the image has been altered. .

According to an embodiment of the invention, the ink powder includes a dye that forms a printed image on a first surface of a substrate, and a pigment that travels or migrates through the substrate to form a latent version of the image that It is visible on a second surface of the substrate. In accordance with one aspect of this embodiment, the ink powder includes a thermoplastic resin binder, a charge control agent, a release agent, as well as the dye and pigment. According to an additional aspect of this embodiment, the ink powder includes a migration-promoting agent. Migration-promoting agents provided by way of example include oils, plasticizers and other polymeric materials. In general, the migration-promoting agent facilitates the migration of the pigment from the first surface of the substrate to the second surface of the substrate, and acts as a solvent for the pigment. Ink powder, in combination with a substrate, such as paper, can be used to produce a secure image that is difficult to falsify and for which it is easy to determine if the image is an original copy of the document by comparing the printed image formed on the first surface of the substrate with the copy, formed with the pigment, of the image visible from the second surface of the substrate.

According to another embodiment of the invention, an ink powder includes a dye that forms a printed image on a first surface of a substrate, and a pigment that travels or migrates through a portion of the substrate and forms a copy of the image that is visible from the first surface of the substrate. The printed image can be compared with the copy formed with the pigment, in order to determine if the original printed image has been altered.

According to a further embodiment of the invention, the ink powder includes a colorless pigment-forming agent and / or a co-reactive, or joint reaction agent, which reacts with the pigment-forming agent to produce a latent image of a printed image

In accordance with yet another embodiment of the invention, a method for forming an ink powder includes blending binder resin particles, mixing coloring particles, charge control agents, release agents, pigment as well as migration agents with Resin particles, cool the mixture, classify the mixture, and dry mix the classified mixture with inorganic materials. In accordance with alternative embodiments of the invention, the ink powder is formed using melt dispersion, dispersion polymerization, suspension polymerization or spray drying.

According to another embodiment of the invention, an image is formed on a substrate by electrostatically transferring an image to a first surface of the substrate and forming a copy of the image that is visible from a second surface of the substrate by applying an ink powder. , which includes a migratory pigment, to the substrate. According to one aspect of this embodiment, the method of forming an image includes providing an ink powder that includes a migration-promoting agent.

Brief description of the figures in the drawings

A more complete understanding of the present invention can be obtained by reference to the detailed description and the claims, considered in connection with the figures, in which the same reference numbers refer to similar elements throughout the figures, and :

Figure 1 illustrates a system, which includes an ink powder according to the present invention, for printing secure documents;

Figure 2 (a) and Figure 2 (b) illustrate a check formed using the ink powder of the present invention;

Figure 3 illustrates a substrate suitable for use with the ink powder of the present invention;

Figure 4 illustrates another substrate suitable for use with the ink powder of the present invention; and Figure 5 illustrates yet another substrate suitable for use with the ink powder of the present invention.

Skilled professionals will appreciate that certain elements of the figures have been illustrated with simplicity and clarity in mind and have not necessarily been drawn to scale. For example, the dimensions of some of the elements of the figures may have been exaggerated in relation to other elements in order to help improve the understanding of the embodiments of the present invention.

Detailed description

The following description has been provided to enable a person skilled in the art to make use of the invention, and discloses the best ways contemplated by the inventors to carry out their invention. Various modifications of the description within the scope of the claimed subject matter will, however, remain clearly evident to those skilled in the art, since the general principles of an ink powder for the formation of ink have been defined herein. Secure images on a document, as well as methods of training and use of the system.

Figure 1 illustrates a system 100 for printing secure documents using the ink powder of the present invention. System 100 includes an ink powder 102 and a substrate 104, which work together to produce a printed image on a first surface 106 of the substrate 104, and a latent copy of the image, underlying the printed image, which is visible from the first (106) and / or the second (108) surfaces of the substrate. Documents formed using system 100 are difficult to falsify and copies of documents are easily detected, because any de-correlation between the printed image and the latent image indicates a falsification, since the lack of a latent image is indicative of a copy of the document

An image is printed on a substrate using the system 100, by transferring the ink powder 102 onto the substrate 104 using, for example, an electrostatic or electrophotographic process. In this case, the ink powder is transferred to a portion of the substrate in order to create a desired image, and the image is melted with the substrate using, for example, heat and / or pressure, and / or a solvent process. in steam A latent image of the printed image is formed as a result of a capillary or chromatographic migration of the pigment to an area underlying the printed surface of the document.

Figure 2 illustrates a check 200 formed using the system 100. Specifically, Figure 2 (a) illustrates an image 202 printed on a first surface 204 of the check, and an image 206 that is formed as a result of the migrating pigment formed on, or visible from, an opposite surface 208 of the check.

Referring again to Figure 1, according to an embodiment of the invention, ink powder 102 includes a thermoplastic binder resin, a dye, a charge control agent and a migratory pigment.

110. Each of the thermoplastic binder resin, the dye and the charge control agent may be the same as those used in conventional ink powders. The ink powder 102 may also include additional ingredients such as a migrating agent 112. The migrating agent 112 may have been configured to help the pigment 110 move or migrate through the substrate and / or help the pigment melt in place, after an initial migration of the pigment - to, for example, mitigate the lateral spread of the pigment. For illustrative purposes, only the pigment and the migrating agent have been illustrated separately in Figure 1. While the ink powder illustrated is a single component ink powder, it is also possible to use ink powder compositions of multiple components (e.g. ink powder and developer agent) to form secure documents as described herein.

The thermoplastic binder resin helps to melt the ink powder with the substrate. According to an embodiment of the invention, the binder resin has a melt index of between about 1 g / 10 min and 50 g / 10 min, at 125 °, and has a glass transition temperature of about 50 ° C and about 65 ° C. Examples of suitable materials for the thermoplastic binder resin include polyester resins, copolymers and / or homopolymers of styrene - for example, styrene acrylates, methacrylates, epoxy resins of styrene-butadiene, latex resins as the base material and similar compounds. By way of a concrete example, the thermoplastic binder resin is a styrene-butadiene copolymer sold by Eliokem as Pliolite S5A resin.

The dye for use with ink powder 102 may be any dye used for electrophotographic image processing, such as iron oxide, other magnetite materials, carbon black, manganese dioxide, copper oxide and aniline black. According to a particular example, the dye is iron oxide marketed by Rockwood Pigments as Mapico Black ("Mapico Black").

The charge control agent helps to maintain a desired charge within the ink powder in order to facilitate the transfer of the image from, for example, an electrostatic drum to the substrate. According to an embodiment of the invention, the charge control agent includes negatively charged control compounds that are charged with metal or with metal-free complex salts, such as copper phthalocyanine pigments, complex aluminum salts, fluoro salts. quaternary ammonium, azo, or azo pigments, of the complex chromium salt type, complex chromium salt and calixarene compounds.

As noted above, the ink powder may also include a release agent such as a wax. The release agent may include low molecular weight polyolefins or derivatives thereof, such as polypropylene wax or polyethylene wax.

Preferred pigments according to the present invention exhibit a strong color absorbency through the

5 substrate 104, good solubility in a migration fluid, and good stability. On the other hand, ambient heat, light and humidity conditions do not negatively affect, preferably, the development properties of ink powder, which is not toxic. In addition, the pigments are preferably indelible. Soluble pigments provided by way of example for ink powder 102 include phenacin, stilbene, nitrous, triarylmethane, diarylmethane, cyanine, perylene, tartracin, xanthene, azo, diazo, triphenylmethane, fluoran, anthraquinone,

10 pyrazolone, quinoline, and phthalocyanine. In accordance with one embodiment of the invention, the pigment is red in color and is formed by xanthene, marketed by BASF under the trade name Baso Red 546, although other color pigments are also suitable for use with this invention.

The ink powder includes a migration-promoting agent, the agent that can be directly incorporated with the other components of the ink powder, or mixed with the pigment and then mixed with the other

15 components of the ink powder, either adsorbed on silica or similar compounds, and then added to the other components of the ink powder, or encapsulated within a material that melts during the melting process, or encapsulated with the pigment

An exemplary ink powder is formed by initially mixing the binder resin particles in the molten state. The dye, the charge control agent (s), the release agent (s), the pigment (s) and the optional migration agent (s) ) are added forming a mixture with the binder resin particles by means of mechanical attrition. The mixture is then cooled and then micronized by air attrition. Micronized particles that are between approximately 0.1 microns and 15 microns in size are classified to extract fine particles, resulting in a finished mixture having particles of a size ranging from about 6 microns to about 15 microns. The classified ink powder is then combined or dry mixed with finely divided particles of inorganic materials such as silica and titania, or titanium oxide. Inorganic materials are added to the surface of the ink powder with the main purpose of improving the flow of the particles of the ink powder, thereby improving the blade cleaning of the photosensitive imaging surface, the temperature is increased blocking or fixing the ink powder, and it helps to load the particles of the ink powder.

Alternatively, the safety ink powder may have been made by other types of mixing techniques that are not described herein in detail. Such alternative methods include melt dispersion, dispersion polymerization, suspension polymerization and spray drying.

The following non-limiting examples illustrate various combinations of materials and procedures useful for forming an ink powder according to various embodiments of the invention. These examples are merely

It is illustrative and it is not intended that the invention be limited to these illustrative examples.

Example (Reference)

The following example illustrates a preparation of an 8 micron safety ink powder for use in electrophotographic printing. An ink powder composition containing the specific composition tabulated below is initially completely premixed and then blended in a molten state in a roller mill 40. The resulting polymer mixture is cooled and then pulverized by means of a Bantam pre-crushing machine (by Hosokawa Micron Powder Systems). The larger crushed particles are converted into ink dust by air attrition and classified into a particle size with a medium volume (measured on a Coulter multi-size meter (Coulter Multisizer)) of approximately 8 microns. The surface of the ink powder is then treated with silica treated with approximately 0.5% of

Dimethyldichlorosilane (commercially available through Nippon Aerosil Co. as Aerosil R976) by dry mixing in a Henschel mixer.

Component

Chemical product Maker Composition examples (parts by weight) Specific composition (parts by weight)

Thermoplastic Binder Resin

Linear polyester Image Polymers-XPE-1965 20-50  46

Load control agent

Aniline  Orient Chemical Company-Bontron NO1 0-3  one

Colorant

Iron oxide Rockwood Pigments Mapico Black 10-50  42

Component

Chemical product Maker Composition examples (parts by weight) Specific composition (parts by weight)

Release agent

Polypropylene Sanyo Chemical Industries-Viscol 330P 0-15  5

Pigment

Organic azo pigment, or azoic Keystone Aniline Corp. Keyplast Red 1-20  6

This single component prepared ink powder is loaded into the appropriate cartridge for the desired printer, such as the Hewlett Packard 5Si printer. An image formed using this ink powder exhibits a density measurement that is greater than 1.40 with a MacBeth densimeter, sharp or defined characters and, initially, no migration of the visible red pigment with a laser-copied paper can be seen. Hammermill standard of 9.14 kg (20 pounds).

Example II (Invention)

The following example illustrates a preparation of an 8 micron safety ink powder that includes a migration agent for use in electrophotographic printing.

Component

Chemical product Maker Composition examples (parts by weight) Specific composition (parts by weight)

Thermoplastic Binder Resin

Linear polyester Image Polymers-XPE-1965 20-50  41

Load control agent

Aniline  Orient Chemical Company-Bontron NO1 0-3  one

Colorant

Iron oxide Rockwood Pigments Mapico Black 10-50  42

Release agent

Polypropylene Sanyo Chemical Industries-Viscol 330P 0-15  5

Pigment

Organic azo pigment Keystone Aniline Corp. Keyplast Red 1-20  6

Oil

MSO Magiesol Oil 1-10 4

The ink powder composition of Example II has been formed in the same manner as the ink powder of Example

10 I, except that a migration agent has been added to the formula. Prepared single component ink powder was retested using a printer such as a Hewlett Packard 5Si printer. The resulting image contained a suitable density, a suitable resolution, lacked appreciable background and, initially, did not show any migration of the visible red pigment. The addition of the migration agent caused the chromatographic process of the visible red pigment / migration agent to be made faster, which caused a

15 decrease in the period of time that the bleeding or impregnation took through, to the back or back of the substrate. Also, the migration agent improved the impregnation throughout the process, by creating a more intense red impregnation through the character, which had a better definition. Again, the ink powder located on the printed side of the paper was removed and a red residual image remained. The total destruction of the document was necessary to remove the red pigment.

20 Example III (Reference)

The following example illustrates a preparation of a security ink powder for Magnetic Ink Character Recognition (MICR) of 10 microns, which includes the specific weight composition tabulated below, for use in printing electrophotographic An ink powder composition containing the specific composition is initially completely mixed and then mixed in a molten state in a roller mill. The resulting polymer mixture is cooled and then pulverized by means of a Bantam pre-crushing machine. The larger crushed particles are converted into ink powder by air attrition, and classified into a particle size with a medium volume (measured on a Coulter multi-size meter ("Coulter Multisizer")) of approximately 10 microns. The surface of the ink powder is then treated with silica treated with approximately 1.0% hexamethyl

disilazane (commercially available through the Nippon Aerosil Co. as Aerosil R8200) by mixing in a Henschel mixer.

Component

Chemical product Maker Composition example (parts by weight) Specific composition (parts by weight)

Thermoplastic Binder Resin

Linear polyester Image Polymers XPE-1965 20-50  46

Load control agent

Aniline  Orient Chemical Company Bontron NO1 0-3  one

Colorant

Iron oxide ISK Magnetics - MO4232 1-30  10

Colorant

Iron oxide Rockwood Pigments -Mapico Black 10-50  32

Release agent

Polypropylene Sanyo Chemical Industries-Viscol 330P 0-15  5

Pigment

Organic azo pigment Keystone Aniline Corp. Keyplast Red 1-20  6

This single component prepared ink powder is loaded into the appropriate cartridge for the desired printer, such as the Hewlett Packard 5Si printer. The resulting image contains a density measurement that is

5 greater than 1.40 in the MacBeth densimeter, high resolution, no appreciable background, and, after initial printing, no migration of the visible red pigment with a standard Hammermill laser copy paper of 9.14 kg (20 pounds) .

For the evaluation of MICR, magnetically encoded documents use an E13-B source, which is the standard source as defined by the American National Standards Institute (ANSI) for verification coding. Magnetic signals from a printed document using the ink powder described above were tested using a RDM Golden Qualifier MICR reader. The ANSI standard for MICR documents that use the E13-B source requires between 50 and 200 percent of the nominal magnetic intensity. The MICR ink powder, formed using the formulation provided above, exhibits a MICR signal having a value of approximately 100

15 percent of the nominal magnetic intensity when printing fully encoded documents.

Example IV (Invention)

The following example illustrates a 10 micron safety ink powder that includes a pigment and a migration fluid according to another embodiment of the invention.

Component

Chemical product Maker Composition example (parts by weight) Specific composition (parts by weight)

Thermoplastic Binder Resin

Linear polyester Image Polymers XPE-1965 20-50  41

Load control agent

Aniline  Orient Chemical Company Bontron NO1 0-3  one

Colorant

Iron oxide ISK Magnetics - MO4232 1-30  10

Colorant

Iron oxide Rockwood Pigments -Mapico Black 10-50  32

Release agent

Polypropylene Sanyo Chemical Industries-Viscol 330P 0-15  5

Pigment

Organic azo pigment Keystone Aniline Corp. Keyplast Red 1-20  6

Component

Chemical product Maker Composition example (parts by weight) Specific composition (parts by weight)

Oil

MSO Magiesol Oil 1-10 5

The ink powder composition of Example IV has been formed in the same manner as the ink powder of Example III, except that a migration agent has been added to the formula. Prepared ink powder of a single component was loaded into a print cartridge by using a suitable printer, such as a Hewlett Packard 5Si printer. The resulting image contained a suitable density, with

5 a measure above 1.40 on a MacBeth densimeter, exhibited an adequate resolution, showed no appreciable background or, initially, no visible pigment migration. The ink powder in this example exhibited a MICR signal of 100 percent of the nominal.

Once it was determined that the MICR signal was acceptable, the indelible safety feature was examined. Again, the migration agent caused the chromatographic process of the visible red pigment / agent to

The migration was done faster, which caused a decrease in the amount of time that the impregnation took through the unprinted side of the document. Also, the migration agent favored the impregnation throughout the process, by creating a more intense red impregnation through the character, which had a better definition. Once again, the ink dust on the printed side of the paper was removed, and a red residual image remained. The total destruction of the document was necessary to remove the red pigment.

The ink powder of the present invention can be used in association with any suitable substrate. For example, ink powder can be used with paper substrates with pulp as the base material, without additional coatings or embedded materials, to form secure images. As a particular example, as noted above, a Hammermill laser copy paper of 9.14 kg (20 pounds) can be used to form safety images with the ink powder of the present invention.

Figures 3-5 illustrate various substrates, including coatings or embedded materials, which are also suitable for printing secure documents using the ink powder of the present invention. More particularly, Figure 3 illustrates a substrate 300 that includes a base 302 and a coating 304 that also includes a migration agent. Figure 4 illustrates a substrate 400, which includes a base 402 and coatings 404 and 406, which also include a migration agent; and Figure 5 illustrates a substrate 500, which also

25 includes a migration agent 504, embedded or mixed in a base 502.

Suitable materials for bases 302, 402 and 502 include paper, such as pulp paper products as the base material. When the substrate is made of papal with pulp as the base material, the paper pulp fibers can be produced in a mechanical, chemical-mechanical or chemical manner. The pulp may have been made of, for example, a lignocellulosic material, such as softwood or hardwood, or it may consist of

30 in a mixture of different pulp fibers, and the pulp can be unbleached, semi-bleached or completely bleached. In addition to pulp fibers, a paper base may contain one or more components that are commonly used in papermaking, such as starch compounds, hydrophobicizing agents, retention agents, shading pigments, fillers and triacetin.

A migration fluid can be any chemical or compound that acts as a solvent for the

35 pigment (for example, pigment 110) and which may be contained within the base or on the base, but without significantly affecting its characteristics. Exemplary migration agents, suitable for coating 304, 404, 406 and for migration agent 504, include oils, plasticizing liquid polymers, or any combination of these components - for example, one or more of: plasticizing agents such as 2,2,4 trimethyl- 1,3 pentanediol diisobutyrate, triacetin, bis (2-ethylhexyl)

Adipate), ditridecyl adipate, adipate ester or phthalate ester; aromatic and aliphatic hydrocarbons such as: carboxylic acids, long chain alcohols, or esters of carboxylic acids and long chain alcohols; as well as liquid polymers such as: the emulsion of polyvinyl alcohols, polyesters, polyethylenes, polypropylenes, polyacrylamides and starches.

When a migration fluid is disposed as a coating on the substrate, as illustrated in Figures 3

45 and 4, any known coating technique can be used, such as bar, engraving, reverse roller, immersion, curtain, slotted head, interstitial, air vein, rotary, spray or similar coating. , in order to form a coating (for example, coating 304) superimposed on a base (for example, base 302). The specific coating technique can be selected as desired and, preferably, provides a coating of migration-promoting agent that is distributed

50 substantially uniformly across a substrate such as a moving band or paper.

The desired amount of the coating containing a migration fluid can be varied from one application to another. By way of a particular example, a substrate includes a single coating applied to a surface, and the amount of coating is from about 0.1 g / m2 to about 20 g / m2 and, preferably, from about 6 g / m2 to about 8 g / m2 Alternatively, in the case that the substrate includes two coatings, as illustrated in Figure 4, it may be desirable to have different coatings favoring migration on each substrate surface. In this case, the coating located on the back surface is between about 0.1 g / m2 and about 20 g / m2, and preferably between about 4 g / m2 and about 5 g / m2, and the obverse coating of the surface is between about 0.1 g / m2 and about 5 g / m2, and preferably between about 2 g / m2 and about 3 g / m2. A desired magnitude or thickness of the coating is determined by factors such as the thickness of the base paper, the porosity of the paper, any pretreatment of the paper and a desired intensity and clarity for an image that is formed with the head or on the back surface of the substrate. For example, if a greater migration of the pigment is desired, the amount of the coating and / or the migration-promoting agent can be increased, and if a lower migration of the pigment is desired, the amount of the coating and / or the promoting agent can be reduced of migration.

The coating that is applied to a paper substrate may contain only a migration-promoting agent. Alternatively, additional chemicals can be added to the coating to, for example, seal or seal the migration fluid, facilitate separation of multiple substrates, from one another, and similar purposes. Additional components of the coating can be applied together with the migration-promoting agent or in an independent deposition step (before or after the application of the migration-promoting agent to the base). For example, the migration fluid may be sealed within the base paper by a wax material such as Kemamide E wax. Alternatively, the coating may include a polymer such as polyvinyl alcohol or polyethylene glycol, in order to provide a barrier between One sheet of paper and the next. The migration fluid, already disposed as a coating on the substrate or embedded within the base, can also be encapsulated within a suitable polymer wrap that breaks during the melting process in the printer. Alternatively, the migration-promoting agent can be absorbed onto a support such as silica, and arranged as a coating on the paper. In the example illustrated in Figure 4, a first coating 404, which is located on a back surface of the substrate, includes a suitable wax and solvents to aid in the application of the coating material (which can evaporate once the coating has been applied base coating), and a second coating includes only the migration-promoting agent and any solvents.

It is possible to make various other modifications, variations and improvements in the design and arrangement of the method and system set forth herein, without departing from the scope of the present invention, as set forth in the accompanying claims.

Claims (18)

1.-A system for producing a secure electrophotographic image, such that the system comprises a substrate and an ink powder that work together to produce a printed image on a first surface of the substrate and an indelible copy of the image, underlying the image printed on the substrate, so that the ink powder has the form of micronized particles comprising: a thermoplastic binder resin; a dye to form an image on the first surface of the substrate; a visible pigment, configured to move or migrate through a portion of the substrate to form an indelible copy of the image on the substrate; Y an agent that favors migration, destined to favor the migration of the pigment into the substrate. 2. The system according to claim 1, wherein the migration-promoting agent comprises a material selected from the group consisting of an oil, a plasticizing agent, a liquid polymer or a combination thereof. 3. The system according to claim 1, wherein the thermoplastic resin comprises a material selected from the group consisting of one or more of the following: polyester resins, styrene homopolymers or copolymers, epoxy resins and resins with latex as base material. 4. The system according to claim 1, further comprising a load control agent. 5. The system according to claim 4, wherein the charge control agent comprises a material selected from the group consisting of copper phthalocyanine pigments, complex aluminum salts, quaternary fluoro-ammonium salts, pigments azo, or azoic, of the type of complex salt of chromium, complex salt of chromium and compounds of calixarene. 6. The system according to claim 1, wherein the dye comprises a material selected from the group consisting of iron oxide, magnetite materials, carbon black, manganese dioxide, copper oxide and aniline black . 7. The system according to claim 1, wherein the visible pigment comprises a material selected from the group consisting of phenacin, stilbene, nitrous, triarylmethane, diarylmethane, cyanine, perylene, tartracin, xanthene, azo, diazo, triphenylmethane, anthraquinone, pyrazolone, quinoline and phthalocyanine. 8. The system according to claim 7, wherein the visible pigment comprises xanthene. 9. The system according to claim 1, wherein the visible pigment is configured such that the pigment moves or migrates from the first surface of the substrate to a second surface of the substrate to form the indelible image in the second surface. 10. The system according to claim 1, wherein the dye includes magnetic material suitable for use with printing techniques with magnetic ink character recognition. 11. The system according to claim 1, wherein the ink powder additionally comprises a release agent. 12. The system according to claim 11, wherein the release agent comprises a material selected from the group consisting of polyolefins and polyolefin derivatives. 13. The system according to claim 1, wherein the ink powder has been configured for use in one of: a developer, or growth system, of a single component, a two-component developer system, or a steam fusion system. 14.- A method for forming an ink powder intended to produce a secure electrophotographic image on a substrate, whereby the substrate and ink powder work together to produce a printed image on a first surface of the substrate, and a copy indelible image, underlying the image printed on the substrate, so that the method comprises the steps of: melt mixing the thermoplastic binder resin particles, adding, forming a mixture, a dye, a visible pigment and a migration-promoting agent for the visible pigment, to the binder resin particles, in order to form a mixture, and Micronize the mixture to provide an ink powder in the form of micronized particles. 15. The method according to claim 14, wherein the step of adding, forming a mixture, comprises mixing by mechanical attrition. 16. The method according to claim 14, wherein the step of micronizing the mixture is performed by air attrition to form the micronized particles. 17. The method according to claim 16, further comprising the step of classifying micronized particles. 18. The method according to claim 17, wherein classifying micronized particles includes segregating particles that are between about 0.1 microns and about 15 microns. 19. The method according to claim 17, further comprising the step of dry mixing the 10 particles classified with inorganic material.